No, don't give him up!!! Give them time... but I can imagine how frustrating this must be!

Yes, like some have said before, Feliway Friends would be worth a try... Also, you could try to rub Jupiter with something that smells familiar to Tinky, maybe a blanket or a towel he has slept on before he has been taken away...?

I also think Tinky feels how stressed everybody is over this situation, poor girl. Pheromones (like in Feliway) might help to make it easier for her!

And too bad for the little kitten! Why does your sister think the house isn't a good place for a kitten?

Another question: When you got Jupiter last year, was Tinky also acting like that? And where they on good terms all the time or did they only tolerate each other?

But I'm sure it has something to do with an unfamiliar scent or stress hormones. I read that cats sometimes act like that when one is coming home from the vet.

Kirsten